Ultrasonic flow rate measurement instrument

ABSTRACT

It is an object to provide an ultrasonic flow amount measuring device in which a direction and position of a transducer can be accurately fixed, thereby improving workability such as a reduction in working time. In order to attain the object, ultrasonic transducers  20  are fixed with a proper interval therebetween using a positioning portion  41  attached to a positioning frame  40 . The position adjustment of the wave transducer  20  is automatically carried out through a positioning spring  25   b  and the positioning portion  41 . A guide frame  30  can be mounted at a proper position on a conduit pipe  10  irrespective of the installation of the wave transducer. The guide frame  30  is mounted without paying attention to an interval between the ultrasonic transducers and coating an acoustic coupling medium on the conduit pipe, so that selection of a setup place, etc. can be freely performed. After pre-assembly, the required acoustic coupling medium is coated on the wave ultrasonic transducers, and the positioning frame  40  is attached to the guide frame  30 , so that the right directions and positions can be applied to the wave ultrasonic transducers.

TECHNICAL FIELD

[0001] The present invention relates to an ultrasonic flow amountmeasuring device. More particularly, the present invention relates to anultrasonic flow amount measuring device having a conduit pipe in whichfluid flows in one direction and a pair of ultrasonic transducersdisposed on an outer surface of the conduit pipe at upstream anddownstream sides thereof in one direction. In the ultrasonic flow amountmeasuring device, one of the ultrasonic transducers transmits anultrasonic wave into the conduit pipe, and the other of the transducersreceives the ultrasonic wave reflected at an inner surface of theconduit pipe. Each of the ultrasonic transducers is positioned correctlyto provide a right direction so that an axis line of the conduit pipe issituated on a propagation plane containing a propagation path of theultrasonic wave, thereby accurately measuring a velocity of the fluidflowing in the conduit pipe.

BACKGROUND OF THE TECHNICAL FIELD

[0002]FIG. 15 is a view for explaining the principle of the ultrasonicflow amount measuring device. In an ultrasonic flow amount measuringdevice 200 shown in FIG. 15, fluid to be measured flows in a directionindicated by an arrow FD in a conduit pipe 60. A pair of ultrasonictransducers 70 is disposed on an outer surface of the conduit pipe 60with a predetermined distance therebetween. Each of the ultrasonictransducers 70 includes a vibrator 71 and a plastic wedge 72. Anacoustically coupling medium 79 for acoustic matching is coated betweenthe wedges 72 and the outer surface of the conduit pipe 60 to enhancepropagation efficiency of the ultrasonic waves. An ultrasonic wavetransmitted from one of the ultrasonic transducers is reflected at aninner surface of the conduit pipe 60, and received by the other of theultrasonic transducers as indicated by a line with arrows shown in FIG.15. A plane containing a propagation path of the ultrasonic wave isreferred to as a propagation plane. The propagation plane corresponds toa sheet face of FIG. 15 containing an axis line of the conduit pipe 60.

[0003] When the ultrasonic transducers 70 are properly oriented andpositioned so that the ultrasonic wave travels on the propagation plane,a time difference At in arrival times at the ultrasonic transducers(propagation time difference) of the ultrasonic wave traveling in aforward direction and a backward direction relative to the flowingdirection is expressed as follows:

Δt=2LV/c ²  (1)

[0004] where V is a velocity of the fluid flowing in the conduit pipe60, L is a length of the propagation path, and c is the speed of sound.From Equation (1), when the propagation time difference At is known froma measurement, the velocity of the fluid is determined. Also, when across-sectional area of the conduit pipe 60 is known, a flow rate of thefluid flowing through the conduit pipe is obtained.

[0005]FIG. 16 is a plan view showing an example of a conventionalultrasonic flow amount measuring device constructed on the basis of theabove-described principle. FIG. 17 is an enlarged plan view showing atransducer shown in FIG. 16, and FIG. 18 is an enlarged front viewshowing a further detail of the transducer shown in FIG. 16. In theultrasonic flow amount measuring device 201 shown in FIG. 16, a guiderail 80 is provided for linearly guiding a pair of ultrasonictransducers 70 parallel to an axial line of the conduit pipe 60. Theguide rail 80 has two frames and is disposed parallel to the axial lineof the conduit pipe 60. The guide rail 80 sandwiches the ultrasonictransducers 70 on side surfaces thereof from both sides. Both ends ofthe guide rail 80 are joined to saddles 81. The saddles 81 are securedto the outer peripheral surface of the conduit pipe 60 by belts 82formed of metal or plastic.

[0006] The ultrasonic transducers 70 are linearly guided along the guiderail 80. The ultrasonic transducers 70 are positioned so thattransmission/reception of the ultrasonic wave is carried out along theline RT with arrows shown in FIG. 15. As shown in FIG. 18, a positioningshaft 78 is vertically provided at a bottom surface of the seat 72 ofeach transducer 70. A screw member (not shown) having a cylindricalshape is provided to be coaxial with the positioning shaft 78, and hasscrew threads formed on inner and outer sides thereof. The screw threadon the outer side of the screw member engages a screw thread formed onan inner side of a position fixing screw 75. The screw thread on theinner side of the screw member engages a screw thread formed on an outerside of a height adjusting screw 76. When the position fixing screw 75is rotated, the guide rail 80 is sandwiched by an upper surface of aplate member (not shown) connected to the bottom portion of the screwmember and the lower surface of the position fixing screw 75.Accordingly, the ultrasonic transducers 70 are fixed so as not to movein the axial direction of the conduit pipe 60. When the height adjustingscrew 76 is rotated, the transducer 70 moves upwardly and downwardlywith respect to the screw member. Accordingly, in the fixing step, adistance between the ultrasonic transducers 70 is adjusted so that acursor 85 attached to each of the ultrasonic transducers 70 ispositioned at a specific position on a scale attached to the guide rail80. Then, each of the ultrasonic transducers 70 is fixed at the positionby the position fixing screw 75, and is closely attached to the uppersurface of the conduit pipe 60 by the height adjusting screw 76.

[0007] In the above-described conventional device, it is necessary toaccurately position the ultrasonic transducers with an appropriatedistance therebetween to place the axial line of the conduit pipe on thepropagation plane of the ultrasonic wave, so that the ultrasonictransducers precisely perform the transmission and reception of theultrasonic wave along the line RT. In the conventional device, thedistance between the ultrasonic transducers is adjusted by positioningthe cursors attached to the ultrasonic transducers based on the scaleattached to the guide rail. The ultrasonic transducers are fixed at theproper positions of the guide rail, and are closely attached to theupper surface of the guide pipe with the fixing screws and the heightadjusting screws. Therefore, it is difficult to fix the ultrasonictransducers with high precision, thereby taking long time and requiringa skilled worker. Further, the acoustic coupling medium is coated on theultrasonic transducers, and the guide rail is fixed on the outer surfaceof the conduit pipe with the belts while positioning. Accordingly, thefixing screws may be loosened to cause a displacement in the distancebetween the ultrasonic transducers. The acoustic coupling medium may beexfoliated or hardened, and the ultrasonic transducers may not closelycontact the conduit pipe, thereby causing an adverse effect.

[0008] In view of the above problems, the present invention has beenmade, and an object of the present invention is to provide an ultrasonicflow amount measuring device in which each of the ultrasonic transducerscan be accurately positioned with a right angle at a right positionwithout difficulty, thereby improving workability and reducing a workingtime.

DISCLOSURE OF THE INVENTION

[0009] In order to achieve the above objects, according to firstinvention, an ultrasonic flow amount measuring device includes a conduitpipe for allowing fluid to flow therein in one direction; a pair ofultrasonic transducers disposed on an outer surface of the conduit pipeat upstream and downstream sides thereof in one direction fortransmitting and receiving an ultrasonic wave propagating along apropagation path in the conduit pipe; and positioning mechanisms forpositioning the ultrasonic transducers with desired angles at desiredpositions so that an axial line of the conduit pipe is situated on apropagation plane containing the propagation path of the ultrasonicwave.

[0010] In the embodiment, the positioning mechanisms are provided forpositioning the ultrasonic transducers with a proper intervaltherebetween. When the ultrasonic transducers are positioned properly,each of the ultrasonic transducers is automatically fixed at a rightposition with a right angle.

[0011] According to the first invention, the positioning mechanism mayinclude a guide frame disposed on the outer surface of the conduit pipefor linearly guiding the ultrasonic transducers in an axial direction ofthe conduit pipe; a positioning frame attached to the guide frame andhaving an outer edge with a saw-tooth shape aligned parallel to theaxial line of the conduit pipe, and positioning means attached to eachof the ultrasonic transducers and having a positioning spring. A tip ofthe positioning spring engages the outer edge of the positioning frame,so that each of the ultrasonic transducers is fixed at the rightposition with the right direction. The outer edge of the positioningframe has recess portions and projecting portions with a constantinterval. Accordingly, when the tip of the positioning spring is fittedin one of the recess portions, the transducer is positioned at one ofpositions with the constant interval (second invention).

[0012] According to the first invention, the positioning mechanism mayinclude a guide frame disposed on the outer surface of the conduit pipefor linearly guiding the ultrasonic transducers in the axial directionof the conduit pipe; a positioning portion integrated with the guideframe and having positioning holes with a constant interval alignedparallel to the axial line of the conduit pipe; and positioning meansfor fixing the ultrasonic transducers with right directions atpredetermined positions by using the positioning holes, thereby makingthe positioning mechanism simple (third invention).

[0013] According to the first invention, the positioning mechanism mayinclude a guide frame mounted on the outer surface of the conduit pipefor linearly guiding the ultrasonic transducers in the axial directionof the conduit pipe, and having plural positioning holes formed on aside surface thereof; and positioning means attached to the ultrasonictransducers and having positioning projections. When each of theultrasonic transducers is mounted on the guide frame, the positioningprojection is fitted into one of the positioning holes at a specificposition, so that the transducer is fixed at the right position with theright angle. Accordingly, when the transducer with the positioning meansis inserted into the guide frame mounted on the conduit pipe, it ispossible to attach the transducer to the guide frame through one-touchoperation (fourth invention).

[0014] According to the second to fourth inventions, the positioningmeans may include a spring member for pressing each of the ultrasonictransducers against the conduit pipe with elastic force when theultrasonic transducers are mounted on the guide frame. In this case, itis not necessary to adjust the ultrasonic transducers to closely contactthe conduit pipe (fifth invention).

[0015] According to the first to fifth inventions, the guide frame maybe attachable to the outer peripheral surface of the conduit pipe in astep before a step of attaching the ultrasonic transducers. Accordingly,it is possible to separately attach the ultrasonic transducers to theguide frame without an effect of a position of an acoustic couplingmedium after the guide frame is attached, thereby reducing a workingtime.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a front view showing an ultrasonic flow amount measuringdevice according to an embodiment 1 of the present invention;

[0017]FIG. 2 is a bottom view of the ultrasonic flow amount measuringdevice shown in FIG. 1;

[0018]FIG. 3 is an enlarged view showing a detail around a positioningshaft of a transducer shown in FIGS. 1 and 2;

[0019]FIG. 4 is a view showing the ultrasonic transducers and apositioning frame of the ultrasonic flow amount measuring device shownin FIG. 1;

[0020]FIG. 5 is a view showing a guide frame and a conduit pipe of theultrasonic flow amount measuring device shown in FIG. 1;

[0021]FIG. 6 is a plan view showing an ultrasonic flow amount measuringdevice according to an embodiment 2 of the present invention;

[0022]FIG. 7 is an enlarged view showing a detail around a positioningshaft of a transducer shown in FIG. 6;

[0023]FIG. 8 is a sectional view taken along line X-X in FIG. 7;

[0024]FIG. 9 is a view showing a case where a disc spring is used inplace of a coil spring shown in FIG. 8;

[0025]FIG. 10 is a front view showing an ultrasonic flow amountmeasuring device according to an embodiment 3 of the present invention;

[0026]FIG. 11 is a bottom view of the ultrasonic flow amount measuringdevice shown in FIG. 10;

[0027]FIG. 12 is an enlarged view showing a detail around a positioningshaft of a transducer shown in FIG. 11;

[0028]FIG. 13 is a sectional view taken along line Y-Y in FIG. 12;

[0029]FIG. 14 is a view showing the transducer in a sub-assembly statebefore the transducer is installed as shown in FIG. 10;

[0030]FIG. 15 is a view for explaining the principle of the ultrasonicflow amount measuring device;

[0031]FIG. 16 is a plan view showing a conventional ultrasonic flowamount measuring device;

[0032]FIG. 17 is an enlarged view showing a transducer and vicinitythereof shown in FIG. 16; and

[0033]FIG. 18 is a front view showing a detailed structure shown in FIG.17.

DESCRIPTION OF REFERENCE NUMERALS

[0034]10 conduit pipe; 20 wave transducer; 25, 26, 27 positioning metalfitting; 25 a, 26 c press plate; 25 b positioning spring; 26 a pressfitting; 26 b fixing pin; 27 a positioning projection; 27 b slit; 28positioning shaft; 28 a E ring; 28 b coil spring; 28 c disc spring; 29acoustic coupling medium; 30, 35 guide frame; 31 saddle; 32 belt; 35 bgraduations; 35 a positioning hole; 40, 50 positioning frame; 41, 51positioning portion; 43 fixing screw; 101, 102, 103 ultrasonic flowamount measuring device.

BEST MODES FOR CARRYING OUT THE INVENTION

[0035] Hereunder, an embodiment 1 of the present invention will beexplained with reference to the accompanying drawings. FIG. 1 is a frontview showing an ultrasonic flow amount measuring device according to anembodiment 1 of the present invention. FIG. 2 is a bottom view of theultrasonic flow amount measuring device shown in FIG. 1. FIG. 3 is anenlarged view showing a detail around a positioning shaft of atransducer shown in FIG. 1. FIG. 4 is a view showing the ultrasonictransducers and a positioning frame of the ultrasonic flow amountmeasuring device shown in FIG. 1. FIG. 5 is a view showing a guide frameand a conduit pipe of the ultrasonic flow amount measuring device shownin FIG. 1.

[0036] In an ultrasonic flow amount measuring device 101 shown in FIGS.1 and 2, a conduit pipe 10 is formed in a cylindrical shape, and fluidto be measured flows through the conduit pipe 10. Ultrasonic transducers20 are respectively disposed on the outer peripheral surface of theconduit pipe 10 at upstream and downstream sides thereof. An ultrasonicwave transmitted from one of the ultrasonic transducers 20 is reflectedat an inner surface of the conduit pipe 10 and received by the other ofthe ultrasonic transducers 20. A guide frame 30 has a pair of platemembers (see FIG. 5) disposed in parallel with an interval therebetweenso that the ultrasonic transducers 20 are inserted between the platemembers. End portions of the plate members are joined with each otherand integrated with saddles 31. The saddles 31 are mounted on the outerperipheral surface of the conduit pipe 10 by belts 32. When theultrasonic transducers 20 are inserted into the space between the platemembers, the guide frame 30 sandwiches the ultrasonic transducers 20from both sides so that the ultrasonic transducers 20 are linearlyguided parallel to an axial line of the conduit pipe 10. A positioningframe 40 has a positioning member 41 having an outer edge formed insaw-teeth shapes (the positioning member 41 is preferably spot-welded onthe positioning frame 40). The positioning member 40 is fixed to theguide frame 30 with fixing screws 43 after the positioning frame 40 isassembled with the ultrasonic transducers 20 (see FIG. 4).

[0037] A positioning metal fitting 25 is used for assembling each of theultrasonic transducers 20. The positioning metal fitting 25 includes apress plate 25 a attached to each of the ultrasonic transducers 20 and apositioning spring 25 b attached to the press plate 25 a. Thepositioning spring 25 b engages proper saw-teeth portions of thepositioning portion 41. Accordingly, when the positioning frame 40assembled with the ultrasonic transducers 20 is attached to the guideframe 30, each of the ultrasonic transducers 20 is automatically fixedat a right position with a right direction. When the positioning frame40 assembled with the ultrasonic transducers 20 is attached to the guideframe 30, the acoustic coupling medium 29 is coated on the surface ofthe conduit pipe 10 where the ultrasonic transducers 20 closely contact,thereby enhancing the propagation efficiency of the ultrasonic wave.

[0038] A preferable specific arrangement of the assembly described abovewill be explained briefly. As shown in FIG. 3, the press plate 25 ahaving the positioning spring 25 b is attached to a support plate (notshown, disposed below the press plate 25 a in FIG. 3) with two fixingscrews 25 c (see FIG. 3) to form the positioning metal fitting 25. Athrough hole is formed at a center of the positioning metal fitting 25for inserting a positioning shaft 28 of each of the ultrasonictransducers 20. In the assembled state described above, the press plate25 a and the support plate sandwich an edge of the positioning frame 40,so that the positioning metal fitting 25 is slidable in the direction ofan arrow LR. The positioning spring 25 b engages the saw-teeth portionsof the positioning portion 41. A coil spring (or disc spring) is mountedon the positioning shaft 28 of each of the ultrasonic transducers 20.The coil spring is positioned between the transducer 20 and thepositioning metal fitting 25, and fixed with an E ring 28 a so that thepositioning shaft 28 does not come out of the positioning metal fitting25 (similar arrangement is shown in FIG. 8). As described above, theultrasonic transducers 20 are fixed to the positioning frame 40 with aright distance therebetween through the positioning portion 41 attachedto the positioning frame 40. Accordingly, it is possible to adjustpositions of the ultrasonic transducers 20 through the positioningsprings 25 b and the positioning portions 41 (in the sub-assembled stateas shown in FIG. 4), thereby making the assembly secure and easy.

[0039] As shown in FIG. 5, the guide frame 30 is mounted on the conduitpipe 10 in an assembly step different from the step of attaching theultrasonic transducers 20 to the positioning frame 40. When the guideframe 30 is mounted as shown in FIG. 5, the ultrasonic transducers 20are not yet attached to the guide frame 30. Accordingly, it is notnecessary to pay attention to the adjustment of the distance between theultrasonic transducers 20, and to coat the acoustic coupling medium onthe conduit pipe 10 as compared with the prior art. Therefore, it ispossible to move and position the guide frame 30 at a desired positionfreely. The assembly work is divided in the two separate steps asdescribed above. As a result, it is not necessary to have a skilledoperator, and it is possible to reduce the number of the steps. Afterthe guide frame 30 is mounted on the conduit pipe 10, the acousticcoupling medium is coated on bottom surfaces of the ultrasonictransducers assembled with the positioning frame 40. Then, theultrasonic transducers 20 are inserted into the guide frame 30, and thepositioning frame 40 is fixed with the fixing screws 43 to complete theassembly.

[0040] An ultrasonic flow amount measuring device according to anembodiment 2 of the present invention will be described next withreference to FIGS. 6 to 8. FIG. 6 is a plan view showing an ultrasonicflow amount measuring device according to the embodiment 2 of thepresent invention. FIG. 7 is an enlarged view showing a detail around apositioning shaft of a transducer shown in FIG. 6. FIG. 8 is a sectionalview taken along line X-X in FIG. 7.

[0041] An ultrasonic flow amount measuring device 102 shown in FIG. 6has the pair of the ultrasonic transducers 20, and a guide frame 50 forguiding the ultrasonic transducers 20. The conduit pipe 10 is formed ina cylindrical shape, and fluid to be measured flows inside the conduitpipe 10. The ultrasonic transducers 20 are disposed on the outerperipheral surface of the conduit pipe 10. The guide frame 50 has a pairof guide plate portions facing with each other and arranged in parallelfor linearly guiding each of the ultrasonic transducers 20. Upper endedges of the guide plate portions are bent at right angle so as to be onthe same plane, and a plurality of positioning holes 51 c is formed in arow in the guide plate portions to form positioning portions 51 a and 51b. The positioning holes 51 c of the positioning portions 51 a and 51 bare formed symmetrically with respect to the centerline of the guideplate portions, and are arranged with a specific pitch. Ends of theguide frame 50 are joined to the saddles 31, and the saddles 31 arefixed to the conduit pipe 10 with the belts 32. The ultrasonictransducers 20 are mounted on the conduit pipe 10, and the contactingsurfaces thereof are coated with the acoustic coupling medium.

[0042] A process of assembling the ultrasonic flow amount measuringdevice 102 will be described next. First, the guide frame 50 is attachedto the conduit pipe 10 with the belts 32. Separately from this step, acoil spring 28 b and a press plate 26 c are attached to the positioningshaft 28 of each of the ultrasonic transducers 20 with an E ring 28 a soas not to come out of the positioning shaft 28. Presser metal fittings26 a of a positioning metal fitting 26 are fixed to the press plate 26 cwith press fitting fixing pins 26 b. The presser metal fittings 26 a areslidable in an arrow direction DS shown in FIG. 8. The presser metalfittings 26 a move to open outwardly in the arrow direction DS (stateshown by 26 a′). The acoustic coupling medium 29 is coated on the bottomsurfaces of the ultrasonic transducers 20. The ultrasonic transducers 20are then inserted into the guide plate portions of the guide frame 50attached to the conduit pipe 10. The press plate 26 c is placed on thepositioning portions 51 a and 51 b. Tip portions of the fixing pins 26 bfitted in the press plate 26 c are matched to proper ones of thepositioning holes 51 c. The presser metal fittings 26 a are moved toclose inwardly in the arrow direction DS, and are fixed to the guideframe 50. In place of the coil spring 28 b shown in FIG. 8, disc springs28 c shown in FIG. 9 may be used.

[0043] In the ultrasonic flow amount measuring device 102 describedabove, the press plates 26 c elastically press the ultrasonictransducers 20 against the outer peripheral surface of the conduit pipe10 along with the coil springs 28 b mounted on the positioning shafts28. It is possible to position the ultrasonic transducers 20 at theright positions with the right directions with the press plates 26 c andthe positioning portions 51 a and 51 b. With the arrangement describedabove, as compared with the ultrasonic flow amount measuring device 101shown in FIG. 1, in the ultrasonic flow amount measuring device 102according to this embodiment, the two components, i.e. the guide frame30 and the positioning frame 40 shown in FIG. 1, are substantiallyreplaced with one component, i.e. the guide frame 50, thereby reducingthe expensive component. The positioning springs 25 b are alsoeliminated, thereby further reducing a cost. Similar to the ultrasonicflow amount measuring device 101 shown in FIG. 1, the assemble work isdivided to achieve the advantages described above.

[0044] An ultrasonic flow amount measuring device according to anembodiment 3 of the present invention will be described next withreference to FIGS. 10 to 14. FIG. 10 is a front view showing theultrasonic flow amount measuring device according to the embodiment 3.FIG. 11 is a bottom view of the ultrasonic flow amount measuring deviceshown in FIG. 10. FIG. 12 is an enlarged view showing a detail around apositioning shaft of a transducer shown in FIG. 11. FIG. 13 is asectional view taken along line Y-Y in FIG. 12. FIG. 14 is a viewshowing the transducer in a sub-assembly state before the transducer isinstalled as shown in FIG. 10.

[0045] The ultrasonic flow amount measuring device 103 shown in FIGS. 10and 11 basically has the same construction as those of the ultrasonicflow amount measuring devices 101 and 102 described above. Theultrasonic flow amount measuring device 103 has a different fixingmechanism for the ultrasonic transducers 20. The ultrasonic flow amountmeasuring device 103 has a guide frame 35 having plural positioningholes 35 a formed in a row on side surfaces thereof. A coil spring 28 dand a positioning metal fitting 27 are mounted on the positioning shaft28 of each of the ultrasonic transducers 20, and are fixed with an Ering 28 a so as not to come out of the positioning shaft 28.

[0046] The ultrasonic transducers 20, the coil springs 28 d and thepositioning metal fittings 27 described above are assembled in advanceas shown in FIG. 14. In this case, the positioning metal fitting 27 ispreferably formed of a plate member having elasticity. The assemblyshown in FIG. 14 is inserted into the guide frame 35. In this case,positioning projections 27 a of the positioning metal fitting 27 arefitted in the positioning holes 35 a of the guide frame 35 (see FIGS.12, 13, and 14), and the positioning metal fitting 27 is attached to theguide frame 35 as shown in FIGS. 10 and 11. In order to fit easily thepositioning projections 27 a into the proper positioning holes 35 a,slits 27 b are formed in the positioning metal fitting 27, andgraduations 35 b are formed on an upper portion of the guide frame 35.When the components are assembled, the acoustic coupling medium 29 iscoated on the bottom surfaces of the ultrasonic transducers 20.

[0047] In the assembled state as described above, the ultrasonictransducers 20 are freely movable in the guide frame 35 in the arrowdirections DL and DR shown in FIG. 13. Accordingly, when the ultrasonictransducers 20 in the assembled state as shown in FIG. 14 is installedin the guide frame 35, the coil springs 28 d press the ultrasonictransducers 20 in the arrow direction DR, and the bottom surfaces of theultrasonic transducers 20 elastically abut against the conduit pipe 10.Accordingly, it is possible to attach the ultrasonic transducers 20 tothe guide frame 35 through one-touch operation, and it is easy to detachthe ultrasonic transducers 20 from the guide frame 35. Similar to theultrasonic flow amount measuring devices 101 and 102, the assemble workcan be divided to achieve the advantages described above.

INDUSTRIAL APPLICABILITY

[0048] According to the present invention, the ultrasonic flow amountmeasuring device is assembled as described above. Therefore, it ispossible to position the ultrasonic transducers with a specificinterval, and automatically fix the ultrasonic transducers at the rightposition with the right direction. Furthermore, the guide frame isattached to the conduit pipe in one step, and the ultrasonic transducersare attached to the positioning frame in another step, thereby improvingthe operation efficiency. For example, it is not necessary to coat theacoustic coupling medium on the conduit pipe when the guide frame isattached to the conduit pipe. Therefore, it is possible to freely moveand position the guide frame at a desired position. Furthermore, whenthe ultrasonic transducers are attached, they are positioned through thepositioning springs and the positioning holes, so that the positioningof the ultrasonic transducers can be easily performed. When thepositioning means having the positioning projection is used, it ispossible to attach the ultrasonic transducers to the guide frame throughone-touch operation, thereby making the assembly process efficient.

What is claimed is:
 1. An ultrasonic flow amount measuring device,comprising: a pair of ultrasonic transducers to be disposed to havecorrect positions and directions on an outer surface of a conduit pipe,through which fluid flows in one direction, at upstream and downstreamsides thereof in a flowing direction so that an ultrasonic wavetransmitted from one of the ultrasonic transducers is reflected at aninner surface of the conduit pipe and is received by the other of theultrasonic transducers, and a propagation plane including a propagationpath of the ultrasonic wave includes an axis line of the conduit pipe,wherein said measuring device includes a positioning mechanism forpositioning the ultrasonic transducers at positions with a desiredinterval so that the ultrasonic transducers are disposed at the correctpositions and directions.
 2. An ultrasonic flow amount measuring deviceaccording to claim 1, wherein said positioning mechanism includes: aguide frame to be attached to the outer surface of the conduit pipe forlinearly guiding the ultrasonic transducers in an axis direction of theconduit pipe, a positioning frame attached to the guide frame and havingan outer edge with a saw-teeth shape parallel to the axial line, andpositioning means attached to the ultrasonic transducers and havingpositioning springs, tips of said positioning springs engaging properportions of the saw-teeth shape of the positioning frame so that theultrasonic transducers are fixed at the correct positions anddirections.
 3. An ultrasonic flow amount measuring device according toclaim 1, wherein said positioning mechanism includes: a guide frame tobe attached to a surface of the conduit pipe for linearly guiding theultrasonic transducers in an axis direction of the conduit pipe, apositioning portion integrated with the guide frame and havingpositioning holes with a predetermined interval parallel to the axialline, and positioning means for fixing the ultrasonic transducers to befixed to the guide frame at desired positions using the positioningholes so that the ultrasonic transducers are fixed at the correctpositions and directions.
 4. An ultrasonic flow amount measuring deviceaccording to claim 1, wherein said positioning mechanism includes: aguide frame to be attached to a surface of the conduit pipe for linearlyguiding the ultrasonic transducers and having plural positioning holesformed on a side thereof, and positioning means attached to theultrasonic transducers and having positioning projections, saidpositioning projections being inserted into proper position holes whenthe ultrasonic transducers are attached to the guide frame so that theultrasonic transducers are fixed at the correct positions anddirections.
 5. An ultrasonic flow amount measuring device according toany one of claims 2 to 4, wherein said positioning means includes aspring member for elastically pressing the transducer against theconduit pipe when the transducer is attached to the guide frame.
 6. Anultrasonic flow amount measuring device according to any one of claims 1to 5, wherein said guide frame is attached to the outer surface of theconduit pipe in a step before the ultrasonic transducers are attached.